#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

#define COMMAND_SIZE 1024
#define FORMAT "[%s@%s %s]# "

// 下面是shell定义的全局数据

#define MAXARGC 128
char *g_argv[MAXARGC];
int g_argc = 0; 

const char *GetUserName()
{
    const char *name = getenv("USER");
    return name == NULL ? "None" : name;
}

const char *GetHostName()
{
    const char *hostname = getenv("HOSTNAME");
    return hostname == NULL ? "None" : hostname;
}

const char *GetPwd()
{
    const char *pwd = getenv("PWD");
    return pwd == NULL ? "None" : pwd;
}

// / /a/b/c
std::string DirName(const char *pwd)
{
#define SLASH "/"
    std::string dir = pwd;
    if(dir == SLASH) return SLASH;
    auto pos = dir.rfind(SLASH);
    if(pos == std::string::npos) return "BUG?";
    return dir.substr(pos+1);
}

void MakeCommandLine(char cmd_prompt[], int size)
{
    //snprintf(cmd_prompt, size, FORMAT, GetUserName(), GetHostName(), DirName(GetPwd()).c_str());
    snprintf(cmd_prompt, size, FORMAT, GetUserName(), GetHostName(), GetPwd());
}

void PrintCommandPrompt()
{
    char prompt[COMMAND_SIZE];
    MakeCommandLine(prompt, sizeof(prompt));
    printf("%s", prompt);
    fflush(stdout);
}

bool GetCommandLine(char *out, int size)
{
    // ls -a -l => "ls -a -l\n" 字符串
    char *c = fgets(out, size, stdin);
    if(c == NULL) return false;
    out[strlen(out)-1] = 0; // 清理\n
    if(strlen(out) == 0) return false;
    return true;
}

// 3. 命令行分析 "ls -a -l" -> "ls" "-a" "-l"
bool CommandParse(char *commandline)
{
#define SEP " "
    g_argc = 0;
    // 命令行分析 "ls -a -l" -> "ls" "-a" "-l"
    g_argv[g_argc++] = strtok(commandline, SEP);
    while((bool)(g_argv[g_argc++] = strtok(nullptr, SEP)));
    g_argc--;
    return true;
}

void PrintArgv()
{
    for(int i = 0; g_argv[i]; i++)
    {
        printf("argv[%d]->%s\n", i, g_argv[i]);
    }
    printf("argc: %d\n", g_argc);
}

int Execute()
{
    pid_t id = fork();
    if(id == 0)
    {
        //child
        execvp(g_argv[0], g_argv);
        exit(1);
    }

    // father
    pid_t rid = waitpid(id, nullptr, 0);
    (void)rid; // rid使用一下
    return 0;
}

int main()
{
    while(true)
    {
        // 1. 输出命令行提示符
        PrintCommandPrompt();

        // 2. 获取用户输入的命令
        char commandline[COMMAND_SIZE];
        if(!GetCommandLine(commandline, sizeof(commandline)))
            continue;

        // 3. 命令行分析 "ls -a -l" -> "ls" "-a" "-l"
        CommandParse(commandline);
        //PrintArgv();

        // 4. 执行命令
        Execute();
    }
    return 0;
}
